We shall further characterize the interphase chromosomes (Benyajati and Worcel, "Isolation, Characterization and Structure of the Folded Interphase Genome of Drosophila melanogaster", 1976, Cell, in press). The isolated genomes will be examined on the E.M. Preliminary observations suggest that the isolated nucleoprotein is in the form of a twisted 110 A chromatin fiber, and only after extensive shearing is the beaded appearance evident (with evently spaced nucleosomes on a 20 A fiber). It is likely that the internucleosome DNA is coiled on the outside of the nucleosomes, just as the intranucleosome DNA is coiled inside (Alberts, Weintraub and Worcel, "A Model for Chromatin Based Upon Two Symmetrically Paired Half Nucleosomes", 1976, Cell, in press). Each single strand nick with DNase I relaxes a supercoiled, nucleosome containing DNA loop (chromomere-sized, B and W, 1976). We shall investigate the nature of the RNA and proteins at the base of the supercoiled DNA loops.